No abstract

The thermal reactions of Clz with the GaAs(lO0) surface were studied using XPS, LEED and thermal desorption spectroscopy. Chlorine uptake at 175 K is initially very rapid, but an extensive corrosion phase is not formed. Five thermd desorption features are seen, with cracking patterns corresponding to GaC1, As*, Gal%, C l a , and ASCL. The implications for the thermal etching of gallium arsenide are discussed.

Atomic-scale images of the (001) surface of monoclinic WO3 have been obtained by scanning tunneling microscopy. Termination of the surface W02 plane with half a monolayer of oxygen ions gives a surface periodicity Q2 times that of the underlying ReO&-like framework. An additional periodicity is introduced by tilting of WO6 octahedra to produce alternately long and short O-O separations along the [110]direction. This produces a (2 X 2) superstructure approximating the space group c2mm. Prominent defect lines at the surface are attributed to missing oxygen ions.Tungsten trioxide (WO3) is an important 5d transitionrnetal oxide that finds application in a number of technologically important devices including thin-film electrochromic displays and H2S gas sensors. The material undergoes at least five phase changes at temperatures between 100 and 1000 K. These are associated with tilting and distortion of a framework of corner-sharing WO6 octahedra to give structures with lower symmetry than the parent cubic structure of

No abstract

No abstract